We don't treat diegetic rewards like magic items, generally, as something earned by the player; those are attached specifically to a character. No one is giving you the vorpal sword for the adventure you weren't there for.
But, certainly over the last few decades, we tend to treat XP (and levels) as being assigned to the player and the campaign; most people aren't making you start again at level 1 when your 10th level character dies. (I know ENWorld has some loud and proud exceptions here.)
Considering your "adventure path" style play and "West marches" style play are philosophically opposed here in how to treat XP, I am curious if the needle is shifting slightly back towards
characters needing to be present to earn their XP.